The leading cause of lower back pain arises from rupture or degeneration of lumbar intervertebral discs. Pain in the lower extremities can be caused by the compression of spinal nerve roots by a bulging disc, while lower back pain is caused by collapse of the disc and by the adverse effects of articulation weight through a damaged, unstable vertebral joint.
In some cases, when a patient having a collapsed disc moves in extension (e.g., leans backward), the posterior portion of the annulus fibrosis or the ligamentum flavum may further compress and extend into the spinal canal. This condition, called “spinal stenosis”, narrows the spinal canal and causes impingement of tissue upon the spinal cord, thereby producing pain.
There have been numerous attempts to provide relief for these afflictions by providing a spacer that inserts between adjacent spinous processes present in the posterior portion of the spinal column. This spacer essentially separates the upper spinous process from the lower spinous process, thereby relieving stenosis. In general, these interspinous implants are adapted to allow flexion movement in the patient, but resist or limit extension.
There are numerous publications disclosing interspinous process spacers having a strut-like body disposed between the spinous processes. See, for example, U.S. Pat. No. 6,451,019; U.S. Pat. No. 6,451,020; U.S. Pat. No. 6,652,527; U.S. Pat. No. 7,201,751, US Patent Publication No. 2005-0240182, US Patent Publication No. 2007-0203495, US Patent Publication No. 2008-0033445, US Patent Publication No. 2008-0058941, US Patent Publication No. 2008-006586, US Patent Publication No. 2008-0086212, US Patent Publication No. 2008-0167656, and US Patent Publication No. 2008-0288075.
US Patent Publication No. 20080167655 (Wang) discloses devices, tools and methods for minimally invasive implantation and distraction between spinous processes for treatment of spinous disorders. Wang discloses an interspinous implant device for distracting at least one pair of adjacent spinous processes includes a main body including a shaft having a longitudinal axis; and first and second parallel arms extending transversely from the main body, wherein at least one of the first and second parallel arms is slidably mounted with respect to the shaft. The parallel arms are configured and dimensioned to extend laterally from both sides of the spinous processes when implanted therebetween and to be inserted between the spinous processes laterally from a single side thereof. The parallel arms are variably positionable between a closed configuration, in which the parallel arms are positioned close to or in contact with one another, to facilitate insertion of the parallel arms between the adjacent spinous processes, and an open configuration, in which the parallel arms are separated from one another.
US Patent Publication No. 2007-0162000 (Perkins) discloses an adjustable spacing device configured to be placed between the spinous processes of at least two adjacent vertebrae and a method of using the device to treat spinal stenosis by restricting extension and allowing normal flexion of adjacent vertebrae relative to one another. Perkins discloses an implant having a horizontal member attached to two legs, one on each side of the spinous process.
US Patent Publication No. 2008-0177271 (Yeh) discloses an implant having a center axle for rotation of the two pieces during insertion. Yeh discloses an interspinous process distraction device including a male distraction element and a female distraction element, which both have a clamping portion for fixedly pushing and rejecting the interspinous processes and also respectively have a first connecting portion and a second connecting portion connected at the other end of the clamping portion. Here, the first connecting portion and the second connecting portion are paired for blocking with each other so as to form the interspinous process distraction device capable of having an opposite rotation. Besides, through clamping two interspinous processes which stress the nerve by the male distraction element and the female distraction element and rotating them to oppositely rotate, the two interspinous processes can therefore be moved to be in alignment as the normal condition.
U.S. Pat. No. 5,393,036 (Sheridan) discloses an implant driven with a screw or threads to create distraction.
U.S. Pat. No. 5,496,318 (Howland) discloses an implant having an H-shape or belt to secure the implant. Howland discloses a spinal fixation device and method for the stabilization of the spine after surgical procedures such as those related to degenerative disc diseases. The device comprises a spacer, which is placed between adjacent vertebrae when installed and a locking mechanism attached to the spacer. The locking mechanism attaches the device to the spinous processes of adjacent vertebrae of the spine in a manner which is non-invasive with respect to the vertebrae to which it is attached.
U.S. Pat. No. 5,092,889 (Forte) discloses an implant held in place by wrapping around the ribs to provide stabilization in compression or distraction.
US Patent Publication Nos. 20090248076 (Reynolds) and 20090248079 (Kwak) each discloses an interspinous spacer having a pair of hooks that, upon lateral insertion between opposed spinous process, bear upon the opposed spinous processes.